fix(dashboard): bound EventsHub delivery with one drop-oldest pump per session

Publish fired a group SendAsync per event and returned, so a slow remote viewer accumulated unbounded pending sends plus cloned MxEvents. Hub delivery now goes through a 256-deep DropOldest channel per hub-watched session with a single drain task and time-bounded sends. The registry counts hub viewers separately and raises HubViewersReleased so the pump is torn down with the last remote viewer; in-process-only sessions start no pump.
2026-10-22 06:13:05 -04:00
parent 488649ce99
commit f1db002b87
5 changed files with 638 additions and 114 deletions
@@ -0,0 +1,52 @@
+using Microsoft.AspNetCore.SignalR;
+
+namespace ZB.MOM.WW.MxGateway.Server.Dashboard.Hubs;
+
+/// <summary>
+/// Time-bounded SignalR send shared by the dashboard hub publishers. A group or
+/// broadcast send completes only once every target connection has accepted the
+/// frame, so one remote viewer with a full transport buffer would otherwise hold
+/// the publisher's single drain loop for as long as that viewer stays slow.
+/// </summary>
+internal static class BoundedHubSend
+{
+    /// <summary>
+    /// Sends <paramref name="argument"/> as <paramref name="method"/> and waits at most
+    /// <paramref name="timeout"/> for it. The timeout cancels the send's own token, so
+    /// the lifetime manager abandons the pending write to the slow connection, and the
+    /// wait itself is bounded too, so a proxy that ignores the token cannot stall the
+    /// caller either.
+    /// </summary>
+    /// <param name="proxy">Target client proxy (a group or all connections).</param>
+    /// <param name="method">Client method name.</param>
+    /// <param name="argument">The single message argument.</param>
+    /// <param name="timeout">Upper bound on the send.</param>
+    /// <param name="stoppingToken">Host shutdown token; its cancellation propagates.</param>
+    /// <returns>
+    /// <see langword="true"/> when the send completed in time; <see langword="false"/>
+    /// when it was abandoned at the timeout.
+    /// </returns>
+    /// <exception cref="OperationCanceledException"><paramref name="stoppingToken"/> was cancelled.</exception>
+    public static async Task<bool> SendAsync(
+        IClientProxy proxy,
+        string method,
+        object argument,
+        TimeSpan timeout,
+        CancellationToken stoppingToken)
+    {
+        using CancellationTokenSource bounded = CancellationTokenSource.CreateLinkedTokenSource(stoppingToken);
+        bounded.CancelAfter(timeout);
+
+        try
+        {
+            await proxy.SendAsync(method, argument, bounded.Token)
+                .WaitAsync(bounded.Token)
+                .ConfigureAwait(false);
+            return true;
+        }
+        catch (OperationCanceledException) when (!stoppingToken.IsCancellationRequested)
+        {
+            return false;
+        }
+    }
+}